Air cushion vehicle

ABSTRACT

Inspection and repair of an air cushion vehicle flexible skirt is carried out with the vehicle supported above a ground surface on support legs projecting from sleeve members built into rigid base structure of the vehicle so as to be open between upper and lower surfaces of the base structure. The vehicle lift system is used to hover the vehicle clear of the ground so that the support legs can be secured in their projecting positions. Alternatively, jacks may be supported over the sleeves and used to force the support legs down the sleeve members to their projecting positions. The vehicle may be further raised above the ground surface to permit inspection and repair of the underside of the rigid base structure by first replacing each support leg with a support stand and pillar assembly and then using the jacks to raise the vehicle with the support legs resting on the pillars.

DESCRIPTION OF INVENTION

This invention relates to air cushion vehicles (A.C.V.) and is moreparticularly concerned with apparatus for supporting an A.C.V. above aground surface when the A.C.V. is non-cushionborne.

Up until the present time each of our A.C.V.'s has been equipped with anumber of landing pads built onto the underside of the A.C.V. rigid basestructure. The number and location of the landing pads is, in general,dictated by the supporting structure, the arrangement of skirtsub-dividers, and the need to be able to land on the crest of a one inten slipway without damaging the bottom of the A.C.V. The number oflanding pads involved varies from four on an A.C.V. of the WinchesterClass (SR.N6) having an all-up weight in the order of 10 tons, and anA.C.V. of the Wellington Class (BH.7) having an all-up weight in theorder of 45 tons, up to seven on an A.C.V. of the Mountbatten Class(SR.N4) having an all-up weight in the order of 200 tons. In addition tothe landing pads, A.C.V.'s of the Winchester and Wellington Classes haveattachment points which allow a separate external jacking system to befitted to lift the A.C.V. for skirt inspection and repair, and they alsohave lifting points to allow the A.C.V. to be slung from a crane or astraddle carrier. On the other hand, a large A.C.V. of the MountbattenClass is generally lifted by hydraulic jacks provided in hard-standingservice areas at shore bases, the jacks lifting the A.C.V. via landingpads, although there is provision for a secondary portable hydraulicsystem to be fitted for emergency lifts when quickness is not of majorconcern.

An A.C.V. at present being designed and being of a size between theWinchester and Wellington A.C.V.'s would demand a large and expensivestraddle carrier for rapid overnight servicing of the A.C.V. flexibleskirt. The external jacking system as used for the Winchester andWellington A.C.V.'s is both expensive and slow in operation in respectto normal civil demands.

It is an object of the present invention to provide apparatus forsupporting an A.C.V. above a ground surface in a non-cushionbornecondition which is inexpensive to manufacture and easy to use.

It is a further object of the invention to provide apparatus forsupporting an A.C.V. above a ground surface in a non-cushionbornecondition which can be carried by the A.C.V. so as to be available foruse at substantially any ground station having a suitable hardstandingarea.

In its broadest aspect the present invention provides apparatus forsupporting an air cushion vehicle above a ground surface in anon-cushionborne condition comprising a plurality of sleeve members eachadapted to be built into rigid base structure of the vehicle so as toextend between an upper end which opens at an upper surface of the rigidbase structure and a lower end which opens at an under surface of therigid base structure, a plurality of support legs adapted to be slidablyreceived one in each sleeve member so as to extend therethrough andproject from the lower end of the sleeve member, and locking means forsecuring each support leg in its projected position relative to thesleeve member.

In another aspect the present invention provides an air cushion vehicleincluding a rigid base structure having an under surface facing towardsa ground surface over which the vehicle operates and an upper surfacefacing away from said ground surface, characterised by a plurality ofsleeve members built into the rigid base structure, and each extendingbetween an upper end which opens at the upper surface of the rigid basestructure and a lower end which opens at the under surface of the rigidbase structure, each sleeve member being adapted to receive a supportleg passed into the upper end of the sleeve member so as to extendtherethrough and project from the lower end of the sleeve member, andlocking means securing each support leg in its projected positionrelative to the sleeve member.

The locking means for each support leg may comprise a split collaradapted for engagement with a flange on the upper end of the sleevemember and a locking ring engageable with the split collar.

Means may be provided for supporting a jack above the upper end of eachsleeve member and a thrust rod projecting externally of the jack may beadapted for co-operation with the support leg so that the vehicle may belifted by extending the jacks and forcing the support legs down.

Whilst the locking means may be incorporated in the jacks by making themirreversible, for example, screw jacks, we prefer that the jacks arehydraulic and that positive locking means are provided for securing thesupport legs in their projected positions relative to the sleevemembers.

Power for the hydraulic jacks may be supplied by a source separate fromthe vehicle or a source on the vehicle, alternatively, the hydraulicjacks could be manually operated.

Support stands may be provided for placement beneath the vehicle when itis supported on the support legs and these support stands may be shapedto fit about the support legs. With the support stands in position thesupport legs may be withdrawn into the vehicle and replaced by pillarswhich co-operate with the support stands. If desired, the vehicle maythen be jacked to a greater height with the support legs resting on thepillars.

The sleeve members built into the rigid base structure are preferablyco-axial with bores through landing pad structures built onto theunderside of the rigid base structure.

To minimise the weight penalty and to ensure that the vehicle restssteadily on uneven ground, we prefer to limit the number of support legsto three, one being on the vehicle longitudinal centerline towards theforward end of the vehicle and the other two being positioned one oneither side of the vehicle longitudinal centerline towards the rear ofthe vehicle.

The invention will now be further described by way of example and withreference to the accompanying drawings, in which:

FIG. 1 is a side elevation of part of the rigid body structure of anA.C.V. with the flexible skirt assembly omitted and the rigid bodystructure broken away in two places to show sleeve members built intothe structure at the positions of landing pads provided on the undersideof the structure;

FIG. 2 is a sectional view of a sleeve and associated landing pad whenthe landing pad is resting on a ground surface with a support leg housedin the sleeve member;

FIG. 3 is a sectional view similar to FIG. 2 with the support legprojecting from the lower end of the sleeve member so as to support theA.C.V. above the ground surface;

FIG. 4 is a sectional view similar to FIG. 3 with a hydraulic jacksupported above the upper end of the sleeve member and a support standpositioned beneath the vehicle so as to partially surround the supportleg; and

FIG. 5 is a sectional view similar to FIG. 4 with the support legretracted and replaced by a pillar which co-operates with the supportstand.

Referring first to FIGS. 1, 2 and 3 of the drawings, FIG. 1 shows partof the rigid body structure 10 of an A.C.V. A flexible skirt normallyattached to the rigid body structure 10 so as to depend downwardlytherefrom and surround the air cushion that in operation is formedbetween the underside of the rigid body structure 10 and a groundsurface 11 is omitted to show landing pads 12 on which the A.C.V. standson the ground surface 11 when non-operational. The landing pads 12 arebuilt onto the under surface of a buoyancy tank structure 13 which formsrigid base structure of the rigid body structure 10. The rigid bodystructure is shown cut away in local areas to reveal sleeve members 14which are built into the buoyancy tank structure 13 so as to extendbetween an upper flanged end 15 which opens above an upper surface ofthe buoyancy tank structure 13 within the rigid body structure 10 and alower end 16 which opens at the under surface of the buoyancy tankstructure 13. Each sleeve member 14 is arranged to be coaxial with abore through the landing pad 12 with which it is associated, wherebycommunication is provided between the interior of the rigid bodystructure 10 and the ground surface 11. In cushionborne operation of theA.C.V. each sleeve member is closed off at its upper flanged end 15 by acapping member (not shown), so that pressurised cushion air does notenter the interior of the rigid body structure 10. The A.C.V. isprovided with three landing pads 12 and associated sleeve members 14,one landing pad and associated sleeve member being located on thelongitudinal centerline of the A.C.V. towards the forward end of theA.C.V. and the other two landing pads and associated sleeve membersbeing positioned towards the rear of the A.C.V. one at either side ofthe longitudinal axis of the A.C.V., only two being visible in FIG. 1.

When the A.C.V. is set down on the ground surface 11, as shown in FIG.1, and it is desired to inspect the flexible skirt assembly for damageor wear, a tubular support leg 18 is slid into each sleeve member 14from the upper flanged end 15 until the lower end of the support leg 18comes to rest on the ground surface 11, as is shown in FIG. 2. Thesupport leg 18 has a closed lower end and an open upper end which isprovided with a flange 19. A split collar 20 having three inwardlyprojecting flanges 21, 22 and 23 is clamped around the upper flanged end15 of the sleeve member 14, so that the flange on the upper end of thesleeve member is housed between the middle and lower flanges 22 and 23,respectively, of the split collar 20, the two halves of the collar beingsecured to each other by studs and nuts (not shown).

The A.C.V. lift system is then switched on and the A.C.V. is hoveredclear of the ground surface 11 so that the support legs 18 slide downthrough the sleeve members 14 and the flange 19 at the upper end of eachsupport leg 18 comes to rest on the upper flanged end 15 of the sleevemember 14 in which the support leg is received. A locking ring 24 havingoutwardly projecting tongues 25 is located over the upper flange 21 ofthe split collar 20 so that the tongues 25 are aligned with cutawayportions in the flange 21 of the split collar 20. The locking ring 24 isthen dropped onto the flange 19 of the support leg 18 and rotated usinga lever (not shown) to locate the tongues 25 beneath the upper flangeportion 21 of the split collar 20, as is shown in FIG. 3. The A.C.V.lift system is switched off so that as the supporting air cushion decaysthe A.C.V. sets down on the support legs 18. The A.C.V. is thensupported with the under surface of the buoyancy tank structure 13 at aheight above the ground surface 11 which is dependent upon the dimensionby which the support legs 18 project from the lower end 16 of the sleevemember 14. This permits the cushion containing flexible skirt (notshown) to hang down without being trapped between the underside of thebuoyancy tank structure 13 and the ground surface 11 so that the skirtcan be inspected and, if necessary, repaired. After any necessary skirtmaintenance, the A.C.V. is again hovered, the locking rings 24 areremoved, and the support legs 18 withdrawn from the sleeve members 14.

Should it be required to raise the A.C.V. on the support legs 18 when nopower is available from the A.C.V. lift system, or the A.C.V. is withinthe confines of a workshop, a hydraulic jack 26 is supported above theupper flanged end 15 of each sleeve member 14 by a yoke member 27 whichis spaced from the split collar 20 by tie rods 28 having opposed endsscrewed into the yoke member 27 and the split collar 20, as shown inFIG. 4, the split collar 20 having first been attached to the upperflanged end 15 of the sleeve member 14 and the support leg 18 slid intothe sleeve member 14 as previously described with reference to FIG. 2.The locking ring 24 is also positioned on the flange 19 at the upper endof the support leg 18 before assembly of the jack 26 and, on assembly, apart of the body portion of the jack 26 together with a projectingthrust rod 29 is passed through the locking ring 24 into the support leg18 so that a ball end 30 provided at the end of the thrust rod 29co-operates with a suitable recess in a cross member 31 fixed internallyof the support leg 18. Hydraulic power is then applied to the jacks 26from a suitable source, such as a generator (not shown) separate fromthe A.C.V., to force the support legs 18 down through the sleeve members14 until the flange 19 at the upper end of each support leg 18 contactsthe flanged upper end 15 of the sleeve member 14. The locking ring 24having simultaneously moved downwardly with the support leg 18 isrotated to lock the support leg 18 in the projecting position.

As is also shown in FIG. 4, a support stand 32 of U-shape when viewed inplan, may be positioned beneath the under surface of the buoyancy tankstructure 13 so as to fit about the support leg 18. With support stands32 in place at the position of each support leg 18, the locking rings 24may be released and the support legs 18 retracted into the sleevemembers 14 so that the A.C.V. sits on the support stands 32. A tubularpillar member 33 may then be positioned in the recessed portion of eachsupport stand 32, as shown in FIG. 5, to replace the support leg 18. Thepillar 33 is held against toppling out of the support stand 32 by a pin34 which passes through aligned holes in lugs 35 on the support stand32. With the lower end of each support leg 18 resting on the upper endof a pillar 33, as shown in FIG. 5, the A.C.V. may be raised furtherabove the ground surface 11 by again using the hydraulic jacks 26 toforce the support legs 18 down through the sleeve members 14 until theflange 19 at the upper end of the support leg 18 again contacts theflanged upper end 15 of the sleeve members 14 when the locking rings 24may again be used to lock the support legs. By this means the A.C.V. isthen supported at twice the height above the ground surface 11 as thatat which it is supported if the support legs 18 are resting on theground surface 11.

Thus the present invention provides simple apparatus for use insupporting an A.C.V. at a first height above a ground surface withoutthe requirement for complex and expensive lifting gear. By making use ofthe A.C.V. lift system to hover the A.C.V. whilst the support legs aresecured in their projecting positions the support legs can be carriedwith the A.C.V. and are available for jacking the A.C.V. at any groundstation having suitable hardstanding.

The hydraulic jacks required to lift the A.C.V. when no power isavailable from the lift system or when it is required to lift the A.C.V.further above the ground surface using the support stands and pillars,together with a generator for supplying hydraulic power to the jacks,can readily be transported by the A.C.V. to a remote ground station foruse whilst the A.C.V. is operating from that station.

Whilst in the embodiment of the invention hereinbefore described withreference to and shown in the accompanying drawings, hydraulic jackshave been described as providing the jacking means, alternative jackingmeans may be provided, such as by screw jacks which being irreversiblecould also constitute the locking means to the exclusion of the lockingrings.

What is claimed is:
 1. An air cushion vehicle (A.C.V.) including a rigidbase structure having an under surface facing towards a ground surfaceover which the vehicle operates and an upper surface facing away fromsaid ground surface, a plurality of sleeve members built into the rigidbase structure and each extending between an upper end which opens atthe upper surface of the rigid base structure and a lower end whichopens at the under surface of the rigid base structure and which isco-axial with a bore through a landing pad structure attached to theunder surface of the rigid base structure, each sleeve member beingadapted to receive a support leg passed into the upper end of the sleevemember so as to extend therethrough and project from the lower end ofthe sleeve member, and locking means for securing each support leg inits projected position relative to the sleeve member.
 2. An A.C.V. asclaimed in claim 1, wherein each locking means comprises a split collaradapted for engagement with a flange on the upper end of the sleevemember and a locking ring engageable with the split collar.
 3. An A.C.V.as claimed in claim 1 or claim 2, further comprising means forsupporting a jack above the upper end of each sleeve member, a thrustrod projecting externally of the jack being adapted for co-operationwith the support leg whereby the vehicle may be lifted by extending thejacks and forcing the legs down.
 4. An A.C.V. as claimed in claim 3,wherein the jacks are hydraulic.
 5. An A.C.V. as claimed in claim 1,further comprising support stands adapted for placement beneath thevehicle when it is supported on the support legs and shaped to fit aboutthe support legs.
 6. An A.C.V. as claimed in claim 5, further comprisingpillars adapted for co-operating with the support stands to replace thesupport legs.
 7. An air cushion vehicle (A.C.V.) including a rigid basestructure having an under surface facing towards a ground surface overwhich the vehicle operates and an upper surface facing away from saidground surface, a plurality of sleeve members built into the rigid basestructure and each extending between an upper end which opens at theupper surface of the rigid base structure and a lower end which opens atthe under surface of the rigid base structure, each sleeve member beingadapted to receive a support leg passed into the upper end of the sleevemember so as to extend therethrough and project from the lower end ofthe sleeve member, and locking means for securing each support leg inits projected position relative to the sleeve member including a splitcollar adapted for engagement with a flange on the upper end of thesleeve member and a locking ring engageable with the split collar.